1. Field of the Invention
The present invention relates to a system for providing dynamic service using optical sub-carrier multiplexing type multi-channel access and method of controlling the same, which provides desired services to subscribers on an active type optical subscriber access network, and is capable of improving the efficiency of use of optical resources of the network.
2. Description of the Prior Art
For methods for providing data service to subscribers over existing telephone lines, x Digital Subscriber Line (xDSL) technologies have been developed and are currently utilized. Additionally, a scheme of providing data service over a cable network using coaxial cables has been proposed and utilized.
Such existing data service technologies do not seem to be problematic in consideration of the amounts of current Internet traffic that subscribers produce. However, as superhigh speed data services, such as telecommuting, distance videoconferencing, High Definition TeleVision (HDTV) rate moving picture service, distance education and telemedicine, are further popularized in the future, it is expected to become more difficult for the existing data service technologies to provide sufficient, high bandwidth, high quality service because the existing data service technologies have bandwidth and distance limitations.
For subscriber access technology for providing high bandwidth service required by users, there is Passive Optical Network (PON) technology. In a PON, a link ranging from an Optical Line Terminator (OLT) to a passive splitter is shared, and branched to a plurality of Optical Network Units (ONUs) in the range of the passive splitter to subscribers. In particular, the PON technology is suitable for broadcast type services. In this PON technology, as to downstream service, a data broadcasting service is naturally provided based on the characteristics of a passive splitter in downstream service, while, as to upstream service, competition arises on the shared link ranging from the OLT to the passive splitter. The provision for a multiplexing scheme is required to solve the problem.
For such a multiplexing scheme, there has been used Time Division Multiple Access (TDMA) in which a shared link is divided and used along a time axis, which is employed in Asynchronous Transfer Mode (ATM)-PON or Ethernet-PON.
TDMA is known as an effective method by which a plurality of subscribers share a single link. TDMA is disadvantageous in that precise synchronization is required to implement TDMA, and the access of subscribers is influenced by the states and requests of other subscribers. Additionally, an increase in overhead due to periodical polling and ranging becomes a burden.
In particular, with the development of Dense Wavelength Division Multiple Access (DWDMA) technology that divides optical resources into sub-resources according to multiple wavelengths, technology for effectively using optical resources is required. For example, Wavelength Division Multiplexing (WDM)-PON has a multichannel support architecture that connects an OLT to an Arrayed Wavelength Guide (AWG) and branches optical resources into sub-resources according to wavelengths between the AWG and the ONU. This architecture is advantageous in terms of the total efficiency of a network. However, the branching is performed according to wavelengths between the ONU and the OLT, so it is meaningless to carry out control according to wavelengths at the OLT. As a result, different multiplexing schemes are employed according to wavelengths.
The Institute of Electrical and Electronics Engineers (IEEE), the International Telecommunications Union (ITU) and the Full Service Access Network (FSAN) have pursued schemes of providing services over an optical fiber-based optical subscriber network, and have proposed Very high bit rate Digital Subscriber Line (VDSL) and the PON. However, in order to implement such service schemes, optical subscriber technology, in which DWDM is directly applied to subscriber equipment, is required. Accordingly, new technology for optical subscriber equipment and optical distribution networks, and a scheme of utilizing optical resources further actively are required.